1. Field of the Invention
The present invention relates to multiple gases installed in cylinders and more particularly to a device and method which permits gases to be automatically mixed when a cylinder is filled.
2. Description of the Prior Art
In the manufacture of industrial gases such as gas mixtures used for welding and the like, it is necessary to mix a specific amount of one or more gases with the active gases. For example, in heliarc welding, the mixture may be 90% helium, argon and 2% oxygen. Another typical industrial mixture is 75% argon and 25% carbon dioxide. The practice in filling cylinders is to identify the quantity of gas with the pressure under which it occurs assuming a standard atmospheric pressure. For example, in a 90% argon, 10% oxygen cylinder, oxygen is introduced into the empty cylinder to a pressure of 246 psi at 70.degree. F. Argon is then introduced until a total pressure of 2,460 psi at 70.degree. F. is reached. It is to be understood that these pressures are a function of temperature and therefore the filler must take this into account. After entering the gases as just described, it will be found that the gases will be stratified and not mixed due to the difference in weights and densities of the gases. Therefore, it is necessary to roll the cylinders for a period of time. To this end, rolling machines are provided upon which the cylinders are placed and rollers then will roll or tumble the cylinders. This requires a certain amount of time which may be from 5 to 30 minutes and also is costly in terms of energy and in damage to the finish of the cylinders, requiring frequent repainting.
Therefore, there has been a long felt need for a device used during the filling operation which automatically provides a homogeneous mixture of the gases in the cylinder.